In our above-mentioned copending application, the contents of which are hereby incorporated by reference, there were disclosed fabrics having novel durable, wavy, pucker or crinkle and dyed effects, contrasting with plain flat background areas, which were produced, for example, in cotton-containing woven or knit fabrics by impregnating the fabric with a polymer-forming, crease-proofing composition which is also capable of crosslinking the cellulose of the cotton fibers, curing the impregnated fabric to condense the polymers and crosslink the cellulose, and applying caustic alkali to selected areas of the fabric to disrupt the cellulose crosslinks and the polymer in those fabric areas. The fabric was then steamed in the substantial absence of tension, neutralized and washed. The resulting product has flat, shrunken areas where the alkali destroyed the polymers and the cellulose crosslinks, and durable, launder-resistant puckered areas where the crosslinks and polymers remained intact and prevented the fabric from shrinking. In addition to imparting an attractive puckered appearance, as disclosed in our copending Ser. No. 657,648, the invention, when applied in suitable patterns, is capable of producing fabrics having good durable press properties combined with superior physical strength and reduced shrinkage. The process is applicable to desized greige, bleached white fabrics, as well as to dyed or printed fabrics. By properly selecting the dyes and dyeing the fabrics before crease-proofing and after alkali treatment, multi-tone effects can be obtained.
As disclosed in Ser. No. 657,648, 100% cotton or high cotton-content fabrics, in which a polymer-forming, crosslinking agent has been installed and cured is treated with a thickened printing paste containing at least 25% caustic to attack the polymeric crosslinking agent, thereby destroying the links and the polymer and unlocking the energy which has been stored in the fibers. As a result, there is induced a massive, dramatic contraction. When the caustic is applied to local selected areas, only the latter shrink, while the remaining, adjacent areas of the fabric retain their crease-resistant, shrink-proof character and their original area dimensions. The result is a cotton or cotton-containing fabric having flat, shrunken areas adjacent to, surrounded by, or themselves surrounding wrinkled or puckered areas, depending on the pattern in which the caustic has been applied.
Since it is also known that cellulosic fabrics, rendered durably press retentive or crease-resistant by means of crosslinking agents suffer from at least about a 40% loss of physical strength, the invention disclosed and claimed in our copending application is capable of resulting in an additional benefit by producing treated fabrics which can approach untreated fabrics in strength. Thus, if the caustic is applied in a pattern, random or otherwise, which pattern comprises a plurality of connected areas, there is formed a continuous matrix of uncrosslinked fibers causing the fabric to have an overall, significant advantage over a similar fabric which has had only the conventional durable press treatment applied to it. Thus, in accordance with the invention disclosed in Ser. No. 657,648, there results a regain in strength so that the ultimate strength loss is no greater than about 10-15%.
The process of the above-referred to invention can be applied, for example, to natural or bleached white fabrics, solid piece-dyed fabrics, multi-tone piece-dyed fabrics, or printed fabrics. By selecting appropriate combinations of alkali-resistant and alkali-sensitive dyes and applying them at predetermined stages of the process, substantially unlimited color combinations of crinkled patterns can be obtained. Furthermore, particular pucker effects can be produced by choosing specially designed yarn or fabric constructions. In addition, manipulation of planned one- or multi-directional fabric tension, combined with subsequently induced chemical-mechanical relaxation, can result in a variety of different degrees of waviness or puckering.
In carrying out the process of our copending application, it was necessary that the caustic-printed, crosslinked fabric be steamed, while in a substantially tension-free state, in order to destroy the crosslinks bridging the cellulose molecules and the polymers in the printed areas to cause the fabric to shrink and to develop the pucker in the caustic-free, unprinted areas. For best results, the steam pucker process requires a steamer in tandem with a printing range.
The process disclosed in our copending application could, in general, frequently be carried out with little capital investment because many plants for finishing fabrics already had the necessary printing and steaming facilities, while resin-treated fabrics were readily obtainable if they were not actually also made on the same premises.
Although the steam pucker process is entirely satisfactory, certain trends in the fabric finishing industry made it desirable to seek a method whereby the steaming step could be eliminated. This search for a method to eliminate the steaming step resulted from a survey which revealed a growing number of plants in which the coincidence of printer-steamer facilities was no longer as widespread as formerly. The present invention not only eliminates the steaming, but also reduces the time of the overall process, thus resulting in a considerable saving of energy and an overall improvement in the economy of the process. Furthermore, because the combination of steam and caustic tend to create a reducing potential to which many dyes are sensitive, elimination of the steaming step now makes it possible to obtain sharper, more brilliant colors with certain dyes.
Among the background prior art discussed in copending Ser. No. 657,648, reference was made to U.S. Pat. No. 2,810,624 (Waddell) which discloses a proposed method involving treating a cellulosic fabric over all its area with an aqueous solution of dimethylolethyleneurea; drying and heat-curing the treated fabric under tension; locally applying a shrinking agent, such as caustic soda; and then washing the fabric. An essential element of the proposed method was that it expressly excluded polymer-forming treating agents and was restricted to the use of dimethylolethyleneurea because that compound was only a crosslinking agent, but did not form insoluble, fiber-ensheathing polymeric coverings or fillings. The shrinking agent could be applied as a thickened, aqueous caustic soda solution at room temperature, somewhat elevated temperatures, or under refrigeration. However, when it is desired to apply the patented process to high count, tight weave fabrics and those containing rayon fibers, a water repellent material is applied to the fabric prior to application of the caustic printing paste to assure sharp outlines and to prevent "wicking" or "feathering", i.e., migration of the caustic paste away from the edges of the printed area.
Another method, proposed in U.S. Pat. No. 3,089,747 (Welch) and limited to the production of pucker effects on regenerated cellulose rayon, involves treating a rayon fabric with a water soluble cellulose ether, a crosslinking agent comprising either an aldehyde or a polyfunctional aldehyde derivative, and an acidic catalyst. After a heat-cure the fabric is printed with a thickened caustic composition and allowed to stand until the pucker developed. Optionally, patentee may add a thermoplastic amine-aldehyde condensation product to the cellulose ether solution to add body to the final product. However, where this is done, the fabric is steamed after application of the caustic paste to develop the desired pucker.
Although the above-described proposals and those additionally discussed in our copending application were asserted by the respective patentees to result in definite improvements in puckered fabrics, the proposed processes do not appear to have achieved commercial success. None of the proposed processes, moreover, was indicated to be applicable to cotton knit fabrics.